1. Field of the Invention
The present invention relates to a broad-band EMP surge arrester in a coaxial line consisting of a casing mounted in the outer conductor and a xcex/4 (or periods thereof) short-circuit line joined in an electrically conductive manner to the inner conductor of the coaxial line, with the end of this short-circuit line making contact with the casing.
2. Description of Related Art
Electromagnetic pulses of the artificial type, such as may be generated by motors, switches, cycled power supply units or the like, as well as those of natural sources, such as those caused by direct or indirect lightning flashes, are conducted by a process of inductive, capacitive or conductive coupling via coaxial lines into the connected equipment, and can damage or even completely destroy them. It is already known how to protect equipment at their input against severe overvoltages, interference voltages or lightning current by means of diverting or reflecting systems. Known examples of such systems are EMP gas arresters, also called EMP charge eliminators, which may be used to divert or reflect these damaging currents, voltages and specific frequencies. Such arrangements are disclosed in Swiss patent CH-660261 and Swiss patent applications 914/95, 158/87.
The protective circuits known to us have various disadvantages. The natural capacity of gas discharge protectors limited their broad-band use to less than 36 Hz, and the known xcex/4 short circuits or periods thereof exhibit bandwidths of up to 20% at most (band-width/mean frequency). This rules out broad-band protection circuits, e.g. for entire waveguide bands or their use in the dual band GSM/PCN (Global System for Mobile Communication/Personal Communication Network).
The object of the invention is to create a broad-band EMP arrester that allows the transmission of a frequency band of a wider bandwidth for example for dual band applications or complete waveguide bands without adversely affecting this frequency band and which reflects or diverts harmful frequencies to earth.
This object is achieved by the invention defined in the claims.
The broad-band EMP surge arrester is a surge arrester, that is used between the casing and an electrically lengthened xcex/4 (or periods thereof) short-circuit line whereby line sections of differing wave impedance arranged in the main conductor make it possible for the frequency band to encompass bandwidths via bandpass transformations of up to an octave in one instance and more than an octave in other instances. The impedance of the main conductor is varied with the corresponding sections. The differences are produced by controlling the parameters of diameter, length and/or surrounding dielectrics of the section of conductor.